A map produced by the Forest Department (Tint and Hla, 1991) shows this area as either closed or degraded forest affected by shifting cultivation. Shifting cultivation is a form of agriculture adapted to upland areas where slopes are steep and soils poor; in such areas, the forest is cut to release nutrients from the resulting biomass to the soil and enhance crop growth. Within a few seasons, this temporary fertility is exhausted and new fields are cut. This process causes a type of deforestation in which natural forest is removed and progressively replaced by secondary forest. When population density is low and the area of forest is relatively large, this process may not be of ecological concern. Yet, as the population grows and expands, and the available forest area shrinks, shifting cultivation can lead to a high level of habitat fragmentation, the complete removal of natural forest, and insufficient time for cleared fields to recover before being cut again; all of these factors lead to a gradual impoverishment of the ecosystem and declining per capita yields (Dearden et al., 1996).
Shifting cultivation is carried out to grow maize and rice for subsistence, and, in isolated areas, opium to generate income to pay for food. Despite the reported increase in poppy cultivation it is probably not a direct cause of deforestation. Given the large labor input required, farmers are more likely to reallocate some of their fields used in subsistence agriculture to grow poppies than to clear new forest areas. This is the case in Shan State, where farmers stop growing upland rice and maize in their less productive fields and use them instead for poppy production. In Kachin State, another factor that mitigates against clearing forests exclusively to grow poppies is a significant reduction in the number of active males in the population due to decades of civil war, and, more recently, the HIV epidemic among drug users.
There is no reliable information on the total area of fields under shifting cultivation in Kachin State. However, in a 24,000-ha area in the Mae Samoeng watershed near Chiang Mai, northern Thailand, a Pathfinder study showed that almost all of the fields are smaller than 10 ha. The vast majority (82 percent) of fields under shifting cultivation are smaller than 5 ha, and half are smaller than 2 ha.
A similar analysis was conducted on 623 clearings to the west of the Nmai Hka. To exclude spurious "clearings" caused by noise in the satellite data and image-to-image registration errors, only clearings greater than or equal to 0.4 ha (5 pixels) were considered. Clearings that were obviously caused by roads or rivers were also excluded, as was a large (1,287 ha) cleared area located on high ground 25 km to the east of the Mali Hka for which there is no obvious explanation. Pixels connected diagonally were treated as contiguous and part of the same clearing.
These results are similar to the size distribution observed in Mae Samoeng, with 95 percent of the clearings smaller than 4 ha. The clearings are therefore presumed to be fields under shifting cultivation.
Copyright © 1998. Logging Burma's Frontier Forests: Resources and the Regime (Washington, DC: World Resources Institute). This posting does not use the adopted name "Myanmar," given to Burma by the State Law and Order Restoration Council (SLORC) in 1988. The name Burma is used in accordance with the Burmese National League for Democracy, the United States Government and many other countries, and leading publications including The Washington Post, Bangkok Post, The Nation, and The Far Eastern Economic Review.